A078311 - OEIS

A078311

Smallest prime factor of n*rad(n)+1, where rad = A007947 (squarefree kernel).

2, 5, 2, 3, 2, 37, 2, 17, 2, 101, 2, 73, 2, 197, 2, 3, 2, 109, 2, 3, 2, 5, 2, 5, 2, 677, 2, 3, 2, 17, 2, 5, 2, 13, 2, 7, 2, 5, 2, 401, 2, 5, 2, 3, 2, 29, 2, 17, 2, 3, 2, 3, 2, 5, 2, 5, 2, 5, 2, 1801, 2, 5, 2, 3, 2, 4357, 2, 3, 2, 13, 2, 433, 2, 5477, 2, 3, 2, 5, 2, 3, 2, 5, 2, 3529, 2, 13

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OFFSET

1,1

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A020639(A078310(n)).

MATHEMATICA

a[n_] := FactorInteger[1 + n * Times @@ FactorInteger[n][[;; , 1]]][[1, 1]]; Array[a, 100] (* Amiram Eldar, Apr 10 2025 *)

PROG

(Haskell)

a078311 = a020639 . a078310 -- Reinhard Zumkeller, Jul 23 2013